A desired belt tension can be set in a belt drive with the help of a tension roller. Hitherto known plastic tension rollers have flat portions on their running surface that are caused by conditions inherent to their manufacturing methods and their base materials. Instead of the desired, fully cylindrical peripheral surface, flattened portions are formed between the ribs of the tension roller wheel with the result that the belt is periodically tightened in the region of the ribs and relaxed in the intervening regions. This causes a vibration excitation with a concomitant disadvantageous noise development of the belt bearing against the running surface of the tension roller wheel.
In tension rollers known from the documents DE 32 26 419 A1 and DE 36 25 800 A1, a plastic wheel is mounted for rotation on a carrier element. In the configuration of the wheel of these documents, an inner ring is arranged exclusively on the peripheral surface of a rolling-bearing outer ring, and said inner ring is connected to an outer ring through radially oriented ribs that are uniformly distributed on the periphery. The tension roller is supported on the belt through the peripheral surface or running surface of the outer ring of the wheel.
Due to the uniformly spaced ribs and the material-related non-circularity, the peripheral surface of the plastic wheel has uniformly configured flattened portions. In certain speed ranges, such a plastic wheel leads to resonance in the belt drive that intensifies wear and running noise.
To avoid these problems, it has already been suggested in DE 44 99 780 C1 that the successive ribs should enclose different angles with each other relative to a center point of the wheel.
The compact spacing of the ribs results in a substantially cylindrical peripheral surface or running surface of the wheel. The short running surface sections between adjacent ribs therefore result in a negligible non-circularity of the peripheral surface. In addition, due to the different angles between the adjacent ribs, the remaining, extremely minor non-circularity is different in each case, so that the occurrence of resonance in the belt drive is prevented for thus obtaining a noise-optimized belt drive.
However, practice has shown that only a relatively limited damping of disturbing vibrations can be achieved with these measures.